In a cellular network, a supplied area is split into cells, each cell being equipped with a base station which serves the mobile stations in that cell. Each cell needs to be uniquely identified if a mobile devices wishes to connect to a cell or if the mobile device is already connected to a cell and wishes to connect to another cell. Cell search/detection is an important procedure for a mobile device deployed in a cellular network. Typically, reference signals are used to identify a cell which needs to be detected by the mobile device during operation. Reference signals are data symbols which are known at the receiver and are used for parameter estimation tasks, e.g. cell-identity (cell-ID) detection.
Apart from reference signals, a control channel such as PBCH is applied in a mobile device and is used for cell selection/re-selection purposes and handover procedures before camping on a cell of the cellular network. In order to gain initial access to an LTE network for example, after completing initial cell synchronization, the mobile device reads the MIB contained in the PBCH. The MIB carries a relatively small amount of important information for the initial access of the mobile device. The MIB is a 24 bit information containing 3 bits for the downlink channel bandwidth in term of resource blocks (RBs), 3 bits for the PHICH (Physical Hybrid-Automatic-Repeat-request Indicator Channel) configuration including PHICH duration and PHICH resource and a System Frame Number (SFN).
The mobile device can obtain an MIB via decoding only after detecting two types of information. As the two types of information are contained in the received PBCH itself, a blind decoding method must be applied which performs all decoding operations in consideration of all possible hypotheses with respect to the two types of information and finds hypotheses having no error in a cyclic redundancy check (CRC). The two types of information is the number of transmit antennas and the transmission frame number on which descrambling operation required for decoding depends on. The number of transmit antennas per frame is three. The total number of times that blind descrambling is required to detect the transmission frame number is four. The transmission frame number relates to the SFN by a modulus four operation, as the same scrambling sequence is applied to every fourth radio frame at the transmitter side.
This results in a total of 12 hypotheses for the blind decoding. Each of the 12 hypotheses may be evaluated by a CRC which itself requires channel decoding, i.e. convolutional decoding, of the PBCH. Convolutional decoding is by far the most computation extensive part. Hence, convolutional decoding must be performed up to 12 times which equals the total number of hypotheses. This consumes power and time.
Hence, what is needed is a solution reduces the blind decoding time.